[U-Boot] [PATCH] dm: gpio: handle GPIO_ACTIVE_LOW flag in DT

[Eric Nelson <eric@nelint.com>]

Hi Simon,

On 04/11/2016 07:59 AM, Simon Glass wrote:
> On 11 April 2016 at 08:55, Eric Nelson <eric@nelint.com> wrote:
>> On 04/11/2016 07:47 AM, Simon Glass wrote:
>>> On 10 April 2016 at 08:48, Eric Nelson <eric@nelint.com> wrote:
>>>> On 04/09/2016 11:33 AM, Simon Glass wrote:
>>>>> On 4 April 2016 at 11:50, Stephen Warren <swarren@wwwdotorg.org> wrote:
>>>>>> On 04/03/2016 08:07 AM, Eric Nelson wrote:
>>>>>>> On 04/02/2016 08:37 PM, Stephen Warren wrote:
>>>>>>>> On 04/02/2016 09:13 AM, Eric Nelson wrote:
>>>>>>>>> On 04/01/2016 10:46 PM, Peng Fan wrote:
>>>>>>>>>> On Thu, Mar 31, 2016 at 01:41:04PM -0700, Eric Nelson wrote:
>>>>>>>>>>> On 03/28/2016 09:57 PM, Peng Fan wrote:
>>>>>>>>>>>> On Fri, Mar 25, 2016 at 01:12:11PM -0700, Eric Nelson wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> Device tree parsing of GPIO nodes is currently ignoring flags.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Add support for GPIO_ACTIVE_LOW by checking for the presence
>>>>>>>>>>>>> of the flag and setting the desc->flags field to the driver
>>>>>>>>>>>>> model constant GPIOD_ACTIVE_LOW.
>>>>>>>>>>>>
>>>>
>>>> <snip>
>>>>
>>>>>>
>>>>>> The intent of the change is good.
>>>>>>
>>>>>> I'm not sure why we need to remove gpio_find_and_xlate(); it provides an API
>>>>>> for clients so they don't need to know how to access driver functionality
>>>>>> through the ops pointer, which I think is an internal/private implementation
>>>>>> detail. Is that detail exposed to clients in other places? If so, removing
>>>>>> the wrapper seems fine. If not, I suspect it's a deliberate abstraction.
>>>>>
>>>>> This seems a bit pedantic, but since Linux does it this way I think we
>>>>> should follow along.
>>>>>
>>>>> Eric you still get to remove the code from all the GPIO drivers - the
>>>>> difference is just creating a common function to call when no xlate()
>>>>> method is available.
>>>>>
>>>>> Can you please take a look at what Stephen suggests?
>>>>>
>>>>
>>>> Got it. I'm just not sure about where to start (before or after
>>>> the patch set you sent) and whether to also remove offset parsing
>>>> from gpio_find_and_xlate().
>>>>
>>>
>>> Which patch did I send? My understanding is:
>>>
>>
>> At the time I sent this, you had just submitted the patch set adding
>> more driver-model support for block devices.
>>
>>         http://lists.denx.de/pipermail/u-boot/2016-April/251095.html
>>
>>> - Add my review/ack tag to the patches as necessary
>>> - Drop the tegra patch
>>> - Update gpio_find_and_xlate() to call a default function if there is
>>> no xlate() method
>>> - Resend the series
>>>
>>> I'm not sure about removing the existing functionality from
>>> gpio_find_and_xlate(), but my guess is that it is best to move it to
>>> your default function, so that gpio_find_and_xlate() doesn't include
>>> any default behaviour in the case where there is a xlate() method.
>>>
>>
>> Reviewing the use of the offset field did yield some information about
>> the broken sunxi support and also that Vybrid was also missing
>> the xlate routine.
>>
>> Since reviewing your patch sets (driver model updates for blk and also
>> driver model updates for mmc) will take some time, so I'll base an
>> updated patch set on master. My guess is that any merge issues will
>> be trivial.
> 
> Yes, that's right.
>>
>> I'll remove your acks in the updated patch set, since the updates
>> to the drivers won't drop the xlate field, but will connect them
>> to the common (__maybe_unused) routine. This will prevent the code
>> from leaking into machines like Tegra that don't need the common code.
> 
> I'm pretty sure you can drop the xlate() implementations from the
> functions, though, and those at the patches I acked.
> 
> I don't think you need __maybe_unused
> 
> static int gpio_find_and_xlate(...)
> {
>    get ops...
> 
>    if (ops->xlate)
>       return ops->xlate(....)
>    else
>       return gpio_default_xlate()...
> }
>
> gpio_default_xlate() (or whatever name you use) should be exported so
> drivers can use it.
> 

This will leak gpio_default_xlate (locally named gpio_xlate_offs_flags)
into machines that don't need it.

I can go the route you suggest above, but it will cost the tegra
and sandbox builds ~64 bytes ;)